Spinal cord modulation for inducing paresthetic and anesthetic effects, and associated systems and methods

ABSTRACT

Spinal cord modulation for inducing paresthetic and anesthetic effects, and associated systems and methods are disclosed. A representative method in accordance with an embodiment of the disclosure includes creating a therapeutic effect and a sensation in a patient by delivering to the patient first pulses having a first set of first signal delivery parameters and second pulses having a second set of second signal delivery parameters, wherein a first value of at least one first parameter of the first set is different than a second value of a corresponding second parameter of the second set, and wherein the first pulses, the second pulses or both the first and second pulses are delivered to the patient&#39;s spinal cord.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 12/765,685, filed Apr. 22, 2010, which claims priority to U.S.Provisional Application 61/171,790, filed on Apr. 22, 2009, both ofwhich are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure is directed generally to spinal cord modulationfor inducing paresthetic and anesthetic effects, and associated systemsand methods.

BACKGROUND

Neurological stimulators have been developed to treat pain, movementdisorders, functional disorders, spasticity, cancer, cardiac disorders,and various other medical conditions. Implantable neurologicalstimulation systems generally have an implantable pulse generator andone or more leads that deliver electrical pulses to neurological tissueor muscle tissue. For example, several neurological stimulation systemsfor spinal cord stimulation (SCS) have cylindrical leads that include alead body with a circular cross-sectional shape and one or moreconductive rings spaced apart from each other at the distal end of thelead body. The conductive rings operate as individual electrodes and, inmany cases, the SCS leads are implanted percutaneously through a largeneedle inserted into the epidural space, with or without the assistanceof a stylet.

Once implanted, the pulse generator applies electrical pulses to theelectrodes, which in turn modify the function of the patient's nervoussystem, such as altering the patient's responsiveness to sensory stimuliand/or altering the patient's motor-circuit output. In pain treatment,the pulse generator applies electrical pulses to the electrodes, whichin turn can generate sensations that mask or otherwise alter thepatient's sensation of pain. For example, in many cases, patients reporta tingling or paresthesia that is perceived as more pleasant and/or lessuncomfortable than the underlying pain sensation. While this may be thecase for many patients, many other patients may report less beneficialeffects and/or results. Accordingly, there remains a need for improvedtechniques and systems for addressing patient pain.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially schematic illustration of an implantable spinalcord modulation system positioned at the spine to deliver therapeuticsignals in accordance with an embodiment of the present disclosure.

FIG. 2 is a flow diagram illustrating a method for treating a patient inaccordance with a particular embodiment of the disclosure.

FIGS. 3A-3F are flow diagrams illustrating further methods for treatinga patient in accordance with further embodiments of the disclosure.

FIG. 4 is a schematic illustration of a representative lead bodysuitable for providing modulation to a patient in accordance withseveral embodiments of the disclosure.

FIGS. 5A-5D illustrate representative wave forms associated with signalsapplied to patients in accordance with particular embodiments of thedisclosure.

FIG. 6 is a partially schematic, cross-sectional illustration of apatient's spine, illustrating representative locations for implantedlead bodies in accordance with embodiments of the disclosure.

DETAILED DESCRIPTION

The present disclosure is directed generally to spinal cord modulationand associated systems and methods that induce, produce, generate, orotherwise cause paresthetic and anesthetic effects in a patient. Suchsystems and methods can be used to treat patient pain. Specific detailsof certain embodiments of the disclosure are described below withreference to methods for modulating one or more target neuralpopulations or sites of a patient, and associated implantable structuresfor providing the modulation. Although selected embodiments aredescribed below with reference to modulating the dorsal root and/orother particular regions of the spinal column to control pain, the leadsmay be in some instances be used to modulate other neurologicalstructures of the spinal cord. Some embodiments can have configurations,components or procedures different than those described in this section,and other embodiments may eliminate particular components or procedures.A person of ordinary skill in the relevant art, therefore, willunderstand that the invention may have other embodiments with additionalelements, and/or may have other embodiments without several of thefeatures shown and described below with reference to FIGS. 1-6.

In general terms, aspects of many of the following embodiments aredirected to producing a sensation (e.g., paresthesia or a parestheticeffect) in the patient, in addition to producing a therapeutic effect(e.g., anesthesia or an anesthetic effect) in the patient. Thetherapeutic effect can be produced by inhibiting, suppressing,downregulating, blocking, preventing, or otherwise modulating theactivity of the affected neural population (e.g., nerve cells). Suchembodiments may be useful in cases for which the patient benefits froman anesthetic effect, but, because the anesthetic effect typicallycreates an absence of pain and/or other sensations, the patient mayrequire the assurance or comfort of a detectable sensation. Bysupplementing the anesthetic effect with a paresthetic effect, which isdetected by the patient, the patient and/or the associated practitionercan better monitor the manner in which the anesthesia-producing signalsare provided. In other embodiments, the patient and/or the practitionermay have other bases for supplementing anesthesia-producing signals withparesthesia-producing signals. Further details are described below withreference to FIGS. 1-6.

FIG. 1 schematically illustrates a representative treatment system 100for providing relief from chronic pain and/or other conditions, arrangedrelative to the general anatomy of a patient's spinal cord 191. Thesystem 100 can include a pulse generator 101, which may be implantedsubcutaneously within a patient 190 and coupled to a signal deliveryelement 110. In a representative example, the signal delivery element110 includes a lead or lead body 111 that carries features fordelivering therapy to the patient 190 after implantation. The pulsegenerator 101 can be connected directly to the lead body 111, or it canbe coupled to the lead body 111 via a communication link 102 (e.g., anextension). Accordingly, the lead 111 can include a terminal sectionthat is releasably connected to an extension at a break 114 (shownschematically in FIG. 1). This allows a single type of terminal sectionto be used with patients of different body types (e.g., differentheights). As used herein, the terms lead and lead body include any of anumber of suitable substrates and/or support members that carry devicesfor providing therapy signals to the patient 190. For example, the leadbody 111 can include one or more electrodes or electrical contacts thatdirect electrical signals into the patient's tissue, such as to providefor patient relief. In other embodiments, the signal delivery element110 can include devices other than a lead body (e.g., a paddle) thatalso direct electrical signals and/or other types of signals to thepatient 190.

The pulse generator 101 can transmit signals to the signal deliveryelement 110 that up-regulate (e.g., stimulate or excite) and/ordown-regulate (e.g., block or suppress) target nerves. As used herein,and unless otherwise noted, the terms “modulate” and “modulation” refergenerally to signals that have either type of effect on the targetnerves. The pulse generator 101 can include a machine-readable (e.g.,computer-readable) medium containing instructions for generating andtransmitting suitable therapy signals. The pulse generator 101 and/orother elements of the system 100 can include one or more processors 107,memories 108 and/or input/output devices. Accordingly, the process ofproviding modulation signals (e.g., electrical signals) and executingother associated functions can be performed by computer-executableinstructions contained on computer-readable media, e.g., at theprocessor(s) 107 and/or memory(s) 108. The pulse generator 101 caninclude multiple portions, elements, and/or subsystems (e.g., fordirecting signals in accordance with multiple signal deliveryparameters), housed in a single housing, as shown in FIG. 1, or inmultiple housings.

The pulse generator 101 can also receive and respond to an input signalreceived from one or more sources. The input signals can direct orinfluence the manner in which the therapy instructions are selected,executed, updated and/or otherwise performed. The input signal can bereceived from one or more sensors 112 (one is shown schematically inFIG. 1 for purposes of illustration) that are carried by the pulsegenerator 101 and/or distributed outside the pulse generator 101 (e.g.,at other patient locations) while still communicating with the pulsegenerator 101. The sensors 112 can provide inputs that depend on orreflect patient state (e.g., patient position, patient posture and/orpatient activity level), and/or inputs that are patient-independent(e.g., time). In other embodiments, inputs can be provided by thepatient and/or the practitioner, as described in further detail later.Still further details are included in co-pending U.S. application Ser.No. 12/703,683, filed on Feb. 10, 2010 and incorporated herein byreference.

In some embodiments, the pulse generator 101 can obtain power togenerate the therapy signals from an external power source 103. Theexternal power source 103 can transmit power to the implanted pulsegenerator 101 using electromagnetic induction (e.g., RF signals). Forexample, the external power source 103 can include an external coil 104that communicates with a corresponding internal coil (not shown) withinthe implantable pulse generator 101. The external power source 103 canbe portable for ease of use.

In another embodiment, the pulse generator 101 can obtain the power togenerate therapy signals from an internal power source, in addition toor in lieu of the external power source 103. For example, the implantedpulse generator 101 can include a non-rechargeable battery or arechargeable battery to provide such power. When the internal powersource includes a rechargeable battery, the external power source 103can be used to recharge the battery. The external power source 103 canin turn be recharged from a suitable power source (e.g., conventionalwall power).

In some cases, an external programmer 105 (e.g., a trial modulator) canbe coupled to the signal delivery element 110 during an initial implantprocedure, prior to implanting the pulse generator 101. For example, apractitioner (e.g., a physician and/or a company representative) can usethe external programmer 105 to vary the signal delivery parametersprovided to the signal delivery element 110 in real time, and selectoptimal or particularly efficacious parameters. These parameters caninclude the position of the signal delivery element 110, as well as thecharacteristics of the electrical signals provided to the signaldelivery element 110. In a typical process, the practitioner uses acable assembly 120 to temporarily connect the external programmer 105 tothe signal delivery device 110. The cable assembly 120 can accordinglyinclude a first connector 121 that is releasably connected to theexternal programmer 105, and a second connector 122 that is releasablyconnected to the signal delivery element 110. Accordingly, the signaldelivery element 110 can include a connection element that allows it tobe connected to a signal generator either directly (if it is longenough) or indirectly (if it is not). The practitioner can test theefficacy of the signal delivery element 110 in an initial position. Thepractitioner can then disconnect the cable assembly 120, reposition thesignal delivery element 110, and reapply the electrical modulation. Thisprocess can be performed iteratively until the practitioner obtains thedesired position for the signal delivery device 110. Optionally, thepractitioner may move the partially implanted signal delivery element110 without disconnecting the cable assembly 120. Further details ofsuitable cable assembly methods and associated techniques are describedin co-pending U.S. application Ser. No. 12/562,892, filed on Sep. 18,2009, and incorporated herein by reference.

During this process, the practitioner can also vary the position of thesignal delivery element 110. After the position of the signal deliveryelement 110 and appropriate signal delivery parameters are establishedusing the external programmer 105, the patient 190 can receive therapyvia signals generated by the external programmer 105, generally for alimited period of time. In a representative application, the patient 190receives such therapy for one week. During this time, the patient wearsthe cable assembly 120 and the external programmer 105 outside the body.Assuming the trial therapy is effective or shows the promise of beingeffective, the practitioner then replaces the external programmer 105with the implanted pulse generator 101, and programs the pulse generator101 with parameters selected based on the experience gained during thetrial period. Optionally, the practitioner can also replace the signaldelivery element 110. Once the implantable pulse generator 101 has beenpositioned within the patient 190, the signal delivery parametersprovided by the pulse generator 101 can still be updated remotely via awireless physician's programmer (e.g., a physician's remote) 111 and/ora wireless patient programmer 106 (e.g., a patient remote). Generally,the patient 190 has control over fewer parameters than does thepractitioner. For example, the capability of the patient programmer 106may be limited to starting and/or stopping the pulse generator 101,and/or adjusting signal amplitude.

In any of these foregoing embodiments, the parameters in accordance withwhich the pulse generator 101 provides signals can be modulated duringportions of the therapy regimen. For example, the frequency, amplitude,pulse width and/or signal delivery location can be modulated inaccordance with a preset program, patient and/or physician inputs,and/or in a random or pseudorandom manner. Such parameter variations canbe used to address a number of potential clinical situations, includingchanges in the patient's perception of pain, changes in the preferredtarget neural population, and/or patient accommodation or habituation.

FIG. 2 is a schematic flow diagram illustrating a process 250 fortreating a patient in accordance with particular embodiments of thedisclosure. The process 250 can include creating both a therapeuticeffect and a sensation in a patient by delivering first pulses (e.g.,first electrical pulses) having a first set of signal deliveryparameters, and second pulses (e.g., second electrical pulses) having asecond set of signal delivery parameters. A first value of at least oneparameter of the first set is different than a second value of acorresponding second parameter of the second set, and the first pulses,second pulses, or both are delivered to the patient's spinal cord. Inparticular embodiments, the effects on the patient may be separatelyattributable to each of the first and second pulses, but in otherembodiments, the effects need not be attributed in such a manner. In oneembodiment, the process 250 can include creating an anesthetic,non-paresthetic effect in the patient by applying first pulses to thepatient's spinal cord in accordance with first signal deliveryparameters (process portion 251). In general, the anesthetic,non-paresthetic effect is one that addresses the patient's pain byblocking or otherwise eliminating the sensation of pain, withoutcreating a sensation for the patient. In particular embodiments, theanesthetic, non-paresthetic effect of the first pulses can have one orboth of the following characteristics. One characteristic is that theanesthetic, non-paresthetic effect is undetected by the patient. Anothercharacteristic is that the anesthetic, non-paresthetic effect produces areduction or elimination of pain.

In process portion 252, a paresthetic effect is created in the patientby applying second pulses to the spinal cord in accordance with secondsignal delivery parameters. In general terms, an aspect of at least oneof the second signal delivery parameters is different than an aspect ofthe corresponding first signal delivery parameter, so as to produce aparesthetic effect rather than an anesthetic, non-paresthetic effect. Inparticular embodiments, the paresthetic effect creates a tingling and/orother patient-detectable sensation. In process portion 253, informationobtained from the patient's feedback to the paresthetic effect is used.For example, the patient and/or practitioner may use this information tounderstand that the system is in an “on” state rather than an “off”state, and/or to determine whether the lead is properly or improperlyplaced, and/or to obtain an indication of the amplitude or signalstrength provided by the system. In other embodiments, the process caninclude obtaining different information and/or taking different actions.Further details of representative methods employing variations of someor all of the foregoing steps are described below with reference toFIGS. 3A-3F.

In some cases, the pain experienced by the patient (and addressed withthe methods and systems of the present disclosure) may not beexperienced by the patient on a continual basis. For example, in someinstances, the patient may experience pain while standing or walking,but not while lying down. In such instances, it can be difficult toaccurately conduct the pre-implant procedure described above withreference to FIG. 1. During such a procedure, the patient is typicallylying down in a prone position while the practitioner adjusts the signaldelivery parameters associated with signals provided by the signaldelivery element (e.g., waveform parameters, active electrodes, and/orthe position of the signal delivery element). FIG. 3A is a schematicflow diagram illustrating a process 350 that can address the foregoingcase. Process 350 can include creating an anesthetic, non-parestheticeffect in a patient by delivering, to a target neural population at thepatient's spinal cord, first pulses having a first set of first signaldelivery parameters, with the anesthetic effect of the first pulsesbeing undetected by the patient. This is an example of the firstcharacteristic described above with reference to FIG. 2. Because theanesthetic effect of the first pulses is undetected by the patient,process 350 can further include creating a patient-detectableparesthetic effect in the patient, concurrent with the anesthetic,non-paresthetic effect (process portion 352). This process can beaccomplished by delivering, to the patient's spinal cord, second pulseshaving a second set of signal delivery parameters. A first value of atleast one first parameter of the first set of signal delivery parametersis different than a second value of a corresponding second parameter ofthe second set, e.g., to produce the paresthetic effect. In thisprocess, the corresponding parameters of the first and second sets areanalogous. For example, if the frequency of the second pulses isdifferent than the frequency of the first pulses to produce aparesthetic effect, the two frequencies can be considered correspondingparameters. Based on patient feedback to the second pulses, the firstsignal delivery parameters are changed (process portion 353), generallyby the practitioner.

As noted above, some patients may experience pain while standing orwalking, but not while lying down. Because the patient is typicallylying down while the practitioner adjusts the signal deliveryparameters, it may not be immediately evident that the parameters arecreating the desired effect in the patient. Accordingly, thepractitioner can position the signal delivery device at a site expectedto produce the desired anesthetic, non-paresthetic effect in thepatient, and can accompany the signals intended to produce that effectwith signals that deliberately produce a patient-detectable parestheticeffect. When the patient begins to report a paresthetic effect, thepractitioner can have an enhanced degree of confidence that the signaldelivery parameters that are common to both the first pulses (whichproduce the anesthetic effect) and the second pulses (which produce theparesthetic effect) are properly selected. These signal deliveryparameters can include the location at which the signal is delivered,the strength (e.g., amplitude) of the signal, and/or other parameters.If, based on patient feedback to the second pulses, the parameter valuescan be improved, the practitioner can change the first signal deliveryparameters, e.g., by moving the lead, applying signals to differentcontacts on the lead, changing signal strength and/or making otheradjustments. In a particular example, this arrangement can reduce thelikelihood that the practitioner will inadvertently increase theamplitude of the anesthesia-producing first pulses to a level that willproduce discomfort and/or muscle activation when the patient changesposition. In other embodiments, other signal delivery parameters may beadjusted, as described further below with reference to FIGS. 3B-3F. Inany of these embodiments, the second signal delivery parameters can alsobe changed, e.g., in parallel with changes to the first signal deliveryparameters, so that the practitioner continues to receive feedback fromthe patient based on the paresthetic effect created by the secondpulses.

FIG. 3B illustrates another representative process 355 for treating apatient, and includes creating an anesthetic, non-paresthetic effect inthe patient (process portion 356), generally similar to process portion351 described above. The anesthetic, non-paresthetic effect is typicallymanifested as a perceived reduction or elimination of pain, and sorepresents an example of the second characteristic described above withreference to FIG. 2. In process portion 357, the process 355 includesproviding an indication of a strength of the first pulses by creating apatient-detectable paresthetic effect in the patient. This can in turninclude delivering to the patient's spinal cord second pulses having asecond set of signal delivery parameters (process portion 358 a), withthe strength of the second pulses being correlated with a strength ofthe first pulses (process portion 358 b) and with a first value of atleast one parameter of the first set being different than a second valueof a corresponding second parameter of the second set (process portion358 c). For example, the frequency of the first pulses may be differentthan the frequency of the second pulses. In process portion 359, thestrengths of the first and second pulses are changed in a parallelmanner. For example, as the strength of the first pulses is increased,the strength of the second pulses can also be increased. Accordingly,when the patient reports a sensation of paresthesia resulting from thesecond pulses, the practitioner can effectively obtain an indication ofthe strength of the first pulses, even though the patient may not beable to report a direct effect of the first pulses. In one aspect ofthis embodiment, the strengths of the first and second pulses may beidentical, and may be changed in identical manners. In otherembodiments, this may not be the case. For example, in a particularembodiment, the practitioner may be aware of a typical offset betweenthe strength of a pulse that is suitable for creating an anestheticeffect and the strength of a pulse that is sufficient to create aparesthetic effect. In such instances, the practitioner may build thisoffset into the manner in which the two sets of pulses are changed topreserve a desired correlation between the onset of a patient-detectableeffect created by the second pulses and an expected anesthetic effectcreated by the first pulses. The amplitude or intensity of the secondpulses can be significantly less than that associated with standard SCSsystems. This can be the case for at least the reason that in at leastsome embodiments, the second pulses are not necessarily intended to maskpain (as they are in standard SCS treatments), but rather are intendedto create a patient-detectable sensation. When this is the case,delivering the second pulses can use less energy than deliveringstandard SCS pulses. In addition to or in lieu of this potentialbenefit, the second pulses can allow the practitioner more flexibilityin setting an appropriate intensity level because a wider range ofintensity levels (e.g., extending to lower values than are associatedwith standard SCS) are expected to produce the desired patientsensation.

In addition to or in lieu of providing feedback that may be used toadjust signal delivery parameters associated with the first pulses(e.g., the anesthesia-producing pulses), aspects of the foregoingprocess may be used to identify faults (e.g., defects, abnormalitiesand/or unexpected states) associated with the system at an early stage.For example, FIG. 3C illustrates a process 360 that includes creating ananesthetic, non-paresthetic effect in the patient (process portion 361)that is undetected by the patient, and that is accompanied by creating apatient-detectable paresthetic effect (process portion 362) generallysimilar to process portion 352 described above. In process portion 363,the amplitudes of the first and second pulses are changed in parallel.In one representative process, the amplitudes are increased and, inother processes, the amplitudes can be decreased.

Process portion 364 includes identifying a fault with the delivery ofthe first pulses based at least in part on the presence or absence of apatient response to the changing amplitude of the second pulses. Forexample, while the patient may be unable to detect whether or not thefirst pulses are being delivered, the practitioner can increase theamplitude of both the first and second pulses to a point at which thepractitioner would expect the patient to report a paresthetic effectcreated by the second pulses. If the patient fails to report such aneffect, the practitioner may be alerted to a fault in the signaldelivery system that applies to both delivery of the first pulses andthe second pulses. Accordingly, the practitioner can rectify the faultand continue the process of establishing suitable signal deliveryparameters for the first pulses, and optionally, the second pulses aswell. The fault may be that the system is not on, that there is anelectrical discontinuity between the signal generator and the leadcontacts, that an element of the signal generator or lead has failed,and/or that the system has another abnormality or unexpectedcharacteristic. In other embodiments, the fault can be identified by thepresence of a patient response, rather than the absence of a patientresponse. For example, if the patient reports a sensation when nosensation is expected (e.g., if the patient reports muscle cramping,sensation and/or stimulation), this may indicate a system fault. Inother cases, this may indicate a misplaced lead, or a patient with alower than expected activation threshold.

FIG. 3D illustrates a process 370 that includes directing both the firstand second pulses to the same target neural population of the patient.Accordingly, process 370 includes creating an anesthetic,non-paresthetic effect in a patient by delivering to a target neuralpopulation at the patient's spinal cord, first pulses having a first setof first signal delivery parameters (process portion 371). The process370 further includes creating a paresthetic effect in the patient bydelivering, to the same target neural population, second pulses havingcharacteristics generally similar to those discussed above withreference to process portion 352 (e.g., at least one parameter valuediffering from a corresponding parameter value of the first pulses). Inthis embodiment, the first and second pulses are delivered to the sametarget neural population, for example, when it is expected that othertarget neural populations may not have a known correlation betweenpatient responses to the second pulses, and patient effects created bythe first pulses. In cases where such a correlation is known, the secondsignals can be applied to a different neural population than the firstpulses. For example, as is discussed further with reference to FIGS. 5Aand 5B, if one neural population is susceptible to paresthesia but notanesthesia, the practitioner may wish to apply the second pulses to adifferent neural population than the first pulses.

FIG. 3E is a flow diagram illustrating a process 365 in which aparesthetic effect is provided to the patient in response to a patientrequest. Process 365 includes creating an anesthetic, non-parestheticeffect in the patient by delivering, to a target neural population atthe patient's spinal cord, first pulses having a first set of firstsignal delivery parameters (process portion 366). Process portion 367includes supplementing the anesthetic, non-paresthetic effect in thepatient with a patient-detectable, paresthetic effect, based on arequest from the patient. This process can in turn include delivering tothe patient's spinal cord, second pulses having a second set of signaldelivery parameters, with a first value of at least one first parameterof the first set being different than a second value of a correspondingsecond parameter of the second set. In a particular embodiment, thepatient may request the second pulses to emulate an effect the patientis already familiar with, as described below with reference to FIG. 3F.

FIG. 3F is a schematic block diagram of a process 375 for treating apatient that, in general terms, includes emulating theparesthesia-inducing effects of a conventional SCS device with a devicethat provides both anesthesia and paresthesia. Accordingly, the process375 can include selecting a patient who previously receivedparesthesia-inducing pulses from a first implanted spinal cordmodulator, and implanting a second spinal cord modulator in that patient(process portion 376). In process portion 377, the second spinal cordmodulator is used to create an anesthetic, non-paresthetic effect in thepatient (process portion 378 a), and also a patient-detectableparesthetic effect (process portion 378 b), using different signaldelivery parameters (process portion 379 a). The signal deliveryparameters can be selected to emulate the paresthesia-inducing pulsesfrom the first implanted spinal cord modulator (process portion 379 b).This arrangement can be used for patients who prefer to retain theparesthetic effect obtained with a conventional SCS device, in additionto obtaining the benefit of an anesthetic effect. The patient may wantthe paresthetic effect for any of a variety of reasons, including butnot limited to the sense of familiarity it may provide, and/or thepleasurable effect of the sensation.

In at least some instances, it may be desirable to the physician orother practitioner to control the amplitude or strength of theanesthesia-producing first pulses, and the patient control the amplitudeor strength of the paresthesia-producing second pulses. Accordingly, thesystem 100 (FIG. 1) delivering the pulses can allow the patient accessto the amplitude control of the second pulses, and restrict access tothe amplitude control of the first pulses to the practitioner. In thismanner, the practitioner can be assured that the anesthetic effect isprovided automatically at a selected level, and the patient can controlat least some aspects of the sensation-producing second pulses. This isa representative example of the more general case in which the amplitude(and/or other parameters) of the first and second pulses are variedindependently of each other. For example, the practitioner may want tovary the frequency of the first pulses while keeping the frequency ofthe second pulses constant. In other embodiments, the practitioner maywant to have the first and second pulses applied with different dutycycles, different pulse widths, different interpulse intervals, and/orother parameters, and so may wish to have independent control over thevalues of these parameters as they apply to the first pulses,independent of the values of the these parameters as they apply to thesecond pulses.

FIG. 4 is a partially schematic illustration of a lead body 111 that maybe used to apply modulation to a patient in accordance with any of theforegoing embodiments. In general, the lead body 111 includes amultitude of electrodes or contacts 120. When the lead body 111 has acircular cross-sectional shape, as shown in FIG. 4, the contacts 120 canhave a generally ring-type shape and can be spaced apart axially alongthe length of the lead body 111. In a particular embodiment, the leadbody 111 can include eight contacts 120, identified individually asfirst, second, third . . . eighth contacts 121, 122, 123 . . . 128. Ingeneral, one or more of the contacts 120 are used to provide signals,and another one or more of the contacts 120 provide a signal returnpath. Accordingly, the lead body 111 can be used to deliver monopolarmodulation (e.g., if the return contact is spaced apart significantlyfrom the delivery contact), or bipolar modulation (e.g., if the returncontact is positioned close to the delivery contact and in particular,at the same target neural population as the delivery contact).

FIG. 5A illustrates a representative electrical signal wave form 540 ahaving first pulses 541 a and second pulses 542 a. In a particularaspect of this embodiment, the first pulses 541 a are provided at ahigher frequency than are the second pulses 542 a. In anotherembodiment, this relationship can be reversed. A single second pulse 542a can be positioned between sequential bursts of the first pulses 541 a(as shown in FIG. 5A), or multiple second pulses 542 a can be providedbetween sequential bursts of the first pulses 541 a. In either of theseembodiments, the first and second pulses 541 a, 542 a can be provided tothe same contact(s) e.g., so that both sets of pulses are directed tothe same target neural population. In such instances, the first andsecond pulses 541 a, 542 a generally do not overlap temporally with eachother. Accordingly, the practitioner can maintain a suitable level ofcontrol over the electric fields produced by each set of pulses.Although the first and second pulses do not overlap, they can beinterleaved with each other in such a manner that the effects of eachset of pulses (e.g., anesthetic and paresthetic effects) can temporarilyoverlap. Put another way, the patient can concurrently receive ananesthetic effect and a paresthetic effect from the interleaved pulses.As discussed above, the first and second pulses can be applied todifferent neural populations in other embodiments.

The first pulses 541 a can be provided at a duty cycle that is less than100%. For example, as shown in FIG. 5A, the first pulses 541 a can beprovided at a duty cycle of about 60%, meaning that the first pulses 541a are active during 60% of the time interval between sequential secondpulses 542 a. The first pulses 541 a can be provided continuously duringeach burst (e.g., each first pulse in a burst can be immediatelyfollowed by another first burst), or an interpulse interval can bepositioned between neighboring first pulses 541 a. In a representativeembodiment, the interpulse interval between first pulses 541 a is 15microseconds, and in other embodiments, the interpulse interval can haveother values, including zero. In the embodiment shown in FIG. 5A, theinterpulse interval between neighboring second pulses 542 a is filled orpartially filled with the first pulses 541 a. The first pulses 541 a canalso include an interphase interval between anodic and cathodic portionsof the pulse. The interphase interval can also be 15 microseconds in arepresentative embodiment, and can have other zero or non-zero values inother embodiments.

In general, the pulse width of the second pulses 542 a can be greaterthan that of the first pulses 541 a (as shown in FIG. 5A). In otherembodiments, the second pulses 542 a can have pulse widths equal to orless than the pulse widths of the first pulses 541 a. The amplitude(e.g., current amplitude or voltage amplitude) of the second pulses 542a can be less than the amplitude of the first pulses 541 a (as shown inFIG. 5A), or equal to the amplitude of the first pulses 541 a, orgreater than the amplitude of the first pulses 541 a (as described belowwith reference to FIG. 5B), depending upon whether or not it isbeneficial to maintain an offset between the respective amplitudes, asdiscussed above with reference to FIG. 3B. In particular examples, thefirst pulses 541 a can be delivered at a frequency of from about 1.5 kHzto about 100 kHz, or from about 1.5 kHz to about 50 kHz. In moreparticular embodiments, the first pulses 541 a can be provided atfrequencies of from about 3 kHz to about 20 kHz, or from about 3 kHz toabout 15 kHz, or from about 5 kHz to about 15 kHz, or from about 3 kHzto about 10 kHz. The amplitude of the first pulses 541 a can range fromabout 0.1 mA to about 20 mA in a particular embodiment, and in furtherparticular embodiments, can range from about 0.5 mA to about 10 mA, orabout 0.5 mA to about 4 mA, or about 0.5 mA to about 2.5 mA. In stillfurther embodiments, the amplitude can be from about 2.0 mA to about 3.5mA, or from about 1 mA to about 5 mA, about 6 mA, or about 8 mA. Thepulse width (e.g., for just the cathodic phase of the pulses) can varyfrom about 10 microseconds to about 333 microseconds. In furtherparticular embodiments, the pulse width of the first pulses 541 a canrange from about 25 microseconds to about 166 microseconds, or fromabout 33 microseconds to about 100 microseconds, or from about 50microseconds to about 166 microseconds. The frequency of the secondpulses 542 a can be in the range of from about 2 Hz to about 1.2 kHz,and in a more particular embodiment, about 60 Hz. The amplitude of thesecond pulses 542 a can be from about 1 mA to about 20 mA, and in aparticular embodiment, from about 2 mA to about 10 mA. The pulse widthof the second pulses 542 a can range from about 10 microseconds to about1,000 microseconds. In a further particular embodiment, the pulse widthof the second pulses can be from about 100 microseconds to about 1,000microseconds, and in a still further particular embodiment, can be about250 microseconds. In at least some embodiments, it is expected that theforegoing amplitudes will be suprathreshold. It is also expected that,in at least some embodiments, the neural response to the foregoingsignals will be asynchronous. For example, the frequency of the firstpulses 541 a can be selected to be higher (e.g., between twice and tentimes higher) than the refractory period of the target neurons at thepatient's spinal cord, which in at least some embodiments is expected toproduce an asynchronous response. Further details of representativesystems and methods for producing asynchronous neural responses areincluded in pending U.S. patent application Ser. No. 12/362,244 filed onJan. 29, 2009 and incorporated herein by reference.

FIG. 5B illustrates another electrical signal 540 b having first pulses541 b and second pulses 542 b. In this particular embodiment, the firstpulses 541 b are provided at a higher duty cycle (e.g., about 85%)compared with that shown in FIG. 5A. The second pulses 542 b are alsoprovided at an amplitude slightly higher than that of the first pulses541 a.

The pulses shown in FIGS. 5A and 5B can be provided to differentpatients, or to the same patient at different times, or the pulses canbe provided to the same patient at the same time, but via differentleads. For example, the patient may be implanted with two leadsgenerally similar to the lead shown in FIG. 4. The first signal 540 a isthen applied to the first and second contacts of one lead, and thesecond signal applied to the first and second contacts of the otherlead. In other embodiments, the signals can be applied in any of a widevariety of manners, e.g., to two 8-contact leads, to one 8-contact leadand two 4-contact leads, to four 4-contact leads, or to other leadarrangements. In any of these embodiments, the second pulses can beapplied to the same target neural population as are the first pulses,e.g., when it is expected that the target neural population will haveboth a paresthetic response and an anesthetic response. In otherembodiments, the second pulses can be applied to a different neuralpopulation than are the first pulses. For example, if the target neuralpopulation to which the first pulses are applied is expected to have ananesthetic response, but not a paresthetic response, the second pulsescan be applied to a different neural population. In such a case, theparesthetic response at the second neural population may still be usedto influence the manner in which the first pulses are applied to thefirst target neural population. Further details of representative leadsand associated systems and methods are included in co-pending U.S.patent application Ser. No. 12/765,747, filed concurrently herewith,titled “Selective High Frequency Spinal Cord Stimulation for InhibitingPain with Reduced Side Effects, and Associated Systems and Methods”, andincorporated herein by reference.

FIG. 5C illustrates still another signal 540 c having spaced-apartbursts of first pulses 541 c. Bursts of second pulses 542 c areinterleaved with the bursts of first pulses 541 c. For example, a singleburst of second pulses 542 c may be positioned between neighboringbursts of first pulses 541 c. This arrangement can be appropriate incases where multiple, uninterrupted second pulses 542 c are suitable forcreating a paresthetic effect, and the resulting separation betweenbursts of the first pulses 541 c does not detract significantly from theanesthetic effect created by the first pulses 541 c.

In one aspect of the embodiment shown in FIGS. 5A and 5B, the first andsecond pulses are the only pulses provided to the corresponding signaldelivery element, and are provided to, for example, the first and secondcontacts 121, 122 of the lead body 110 shown in FIG. 4. In otherembodiments, these signals may be applied to other contacts orcombinations of contacts. For example, FIG. 5D illustrates an embodimentin which a first signal 540 d applies corresponding first and secondpulses 541 d, 542 d to a selected pair of contacts (e.g., the first andsecond contacts 121, 122 shown in FIG. 4) and a second signal 540 eapplies first and second pulses 541 e, 542 e to another pair of contacts(e.g., the seventh and eighth contacts 127, 128 shown in FIG. 4). Thehigh frequency first pulses 541 d, 541 e are provided simultaneously ateach pair of contacts, while the low second frequency pulses 542 d, 542e are staggered in time and location. This arrangement may be used whenthe practitioner wishes to provide a broader field with the first pulses541 d, 541 e. In other embodiments, the first and second pulses may beprovided to other contacts, and/or in accordance with other timingpatterns, based generally on a patient-specific basis.

In any of the foregoing embodiments, the signal delivery parametersselected for any of the first pulses 541 a-e (referred to collectivelyas first pulses 541) and the second pulses 542 a-e (referred tocollectively as second pulses 542) can be selected to produce ananesthetic, non-paresthetic effect, and a paresthetic effect,respectively. As discussed above, in at least some embodiments, thefirst pulses 541 will be provided at a higher frequency than the secondpulses 542. For example, the first pulses 541 can be provided at afrequency of from about 1.5 kHz to about 50 kHz, while the second pulses542 can be provided in a range of from about 2 Hz to about 1.2 kHz. Inother embodiments, the pulses can have different relationships. Forexample, the second pulses 542 can be within a 3 kHz to 10 kHz range,but at a frequency less than the first pulses 541.

FIG. 6 is a cross-sectional illustration of the spinal cord 191 and anadjacent vertebra 195 (based generally on information from Crossman andNeary, “Neuroanatomy,” 1995 (published by Churchill Livingstone)), alongwith selected representative locations for representative lead bodies110 (shown as lead bodies 110 a-110 d) in accordance with severalembodiments of the disclosure. The spinal cord 191 is situated between aventrally located ventral body 196 and the dorsally located transverseprocess 198 and spinous process 197. Arrows V and D identify the ventraland dorsal directions, respectively. In particular embodiments, thevertebra 195 can be at T9, T10, T11 and/or T12 (e.g., for axial low backpain and/or leg pain) and in other embodiments, the lead bodies can beplaced at other locations. The lead body can be positioned to providethe same or different pulses to different vertebral levels (e.g., T9 andT10). The spinal cord 191 itself is located within the dura mater 199,which also surrounds portions of the nerves exiting the spinal cord 191,including the dorsal roots 193 and dorsal root ganglia 194.

The lead body is generally positioned to preferentially modulate tactilefibers (e.g., to produce the paresthetic effect described above) and toavoid modulating fibers associated with nociceptive pain transmission.In a particular embodiment, a lead body 110 a can be positionedcentrally in a lateral direction (e.g., aligned with the spinal cordmidline 189) to provide signals directly to the spinal cord 191. Inother embodiments, the lead body can be located laterally from themidline 189. For example, the lead body can be positioned just off thespinal cord midline 189 (as indicated by lead body 110 b), and/orproximate to the dorsal root 193 or dorsal root entry zone 188 (e.g.,1-4 millimeters from the spinal cord midline 189, as indicated generallyby lead body 110 c), and/or proximate to the dorsal root ganglion 194(as indicated by lead body 110 d). Other suitable locations for the leadbody 110 include the “gutter,” also located laterally from the midline189. In still further embodiments, the lead bodies may have otherlocations proximate to the spinal cord 191 and/or proximate to othertarget neural populations, e.g., laterally from the midline 189 andmedially from the dorsal root ganglion 194. In any of the foregoingembodiments, electrical pulses may be applied to the lead body 110 toprovide both a paresthetic and an anesthetic effect, as described above.As discussed above, the patient can be implanted with a single lead body(e.g., one of the lead bodies 110 a-110 d) or multiple lead bodies(e.g., combinations of the lead bodies 110 a-110 d).

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from theinvention. For example, the signal delivery parameters may have valuesother than those specifically described above, but which are alsoselected to produce anesthetic or paresthetic effects in the mannerdescribed above. Particular embodiments were described above in thecontext of signals applied to the patient's spinal cord, but in otherembodiments, signals (e.g., signals creating an anesthetic,non-paresthetic effect, and/or signals creating a paresthetic effect)can be applied to other neural populations, including, but limited to,peripheral nerves. For example, such methods can include applying firstpulses to the patient's spinal cord to create an anesthetic,non-paresthetic effect, and applying second pulses to a peripheral nerveto create a paresthetic effect. Systems suitable for carrying outembodiments of the foregoing techniques are included in co-pending U.S.application Ser. No. 12/765,790, filed concurrently herewith, titled“Devices for Controlling High Frequency Spinal Cord Stimulation forInhibiting Pain, and Associated Systems and Methods”, and incorporatedherein by reference.

Certain aspects of the invention described in the context of particularembodiments may be combined or eliminated in other embodiments. Forexample, the wave forms described above with reference to FIGS. 5A-5Dmay be combined in further embodiments. In addition, while advantagesassociated with certain embodiments have been described and the contextof those embodiments, other embodiments may also exhibit suchadvantages. Not all embodiments need necessarily exhibit such advantagesto fall within the scope of the present disclosure. Accordingly, thedisclosure and associated technology can encompass other embodiments notexpressly shown or described herein.

We claim:
 1. A patient treatment system, comprising: an implantablepulse generator coupleable to an implantable signal delivery device andhaving a controller programmed with instructions for: directing a first,non-paresthesia generating electrical signal to the implantable signaldelivery device to create an anesthetic effect in a patient, the firstelectrical signal having a first set of first signal deliveryparameters, including a frequency in a frequency range from 1.5 kHz to100 kHz, and a pulse width in a pulse width range of 10 microseconds to333 microseconds; and directing a second electrical signal to the signaldelivery device, the second electrical signal having a second set ofsecond signal delivery parameters, including a frequency in a frequencyrange from 2 Hz to 1.2 kHz.
 2. The system of claim 1, further comprisingthe implantable signal delivery device, wherein the implantable signaldelivery device has a plurality of electrodes configured to be implantedwithin the patient's epidural space, proximate to one or more targetneural populations in the patient's spinal cord, and wherein thecontroller is programmed with instructions for: delivering to the signaldelivery device bursts of the first electrical pulses having a frequencyin a first frequency range of from 1.5 kHz to 50 kHz, to create ananesthetic, non-paresthetic effect in the patient; and delivering to thesignal delivery device the second electrical pulses to create aparesthetic effect in the patient, wherein the second electrical pulsesinclude a single second pulse during an interval between sequentialbursts of the first electrical pulses.
 3. The system of claim 2 whereinthe controller includes instructions for directing the first pulses to afirst electrode of the signal delivery device and directing the secondpulses to a second electrode of the signal delivery device, wherein thesecond electrode is different from the first electrode.
 4. The system ofclaim 2 wherein the controller is programmed with instructions fordirecting the first and second pulses sequentially to the same electrodeof the signal delivery device.
 5. The system of claim 2 wherein thefirst and second pulses have different pulse widths.
 6. The system ofclaim 2 wherein the first pulses have a first pulse width and whereinthe second pulses have a second pulse width, and wherein the secondpulse width is greater than the first pulse width.
 7. The system ofclaim 1 wherein the first set of first signal delivery parametersincludes a frequency of from 3 kHz to 10 kHz, and the second set ofsecond signal delivery parameters includes a frequency of from 20 Hz to1.2 kHz.
 8. The system of claim 1 wherein the first set of first signaldelivery parameters includes a pulse amplitude of from 0.5 mA to 4 mA.9. The system of claim 1 wherein the first set of first signal deliveryparameters includes pulse widths between 33 microseconds and 100microseconds, inclusive.
 10. The system of claim 1 wherein the secondset of second signal delivery parameters includes a pulse amplitude offrom 2 mA to 10 mA.
 11. The system of claim 1 wherein the controller isprogrammed with instructions for directing the first pulses inaccordance with a duty cycle.
 12. The system of claim 1 wherein thecontroller further includes instructions for receiving first updates tothe first signal delivery parameters and second, independent updates tothe second signal delivery parameters.
 13. The system of claim 1 whereinthe first set of first signal delivery parameters includes a frequencyof from 3 kHz to 20 kHz.
 14. The system of claim 1 wherein the first setof first signal delivery parameters includes a frequency of from 3 kHzto 15 kHz.
 15. The system of claim 1 wherein the first set of firstsignal delivery parameters includes a frequency of from 5 kHz to 15 kHz.16. The system of claim 1 wherein the first set of first signal deliveryparameters includes a pulse amplitude of from 0.1 mA to 20 mA.
 17. Thesystem of claim 1 wherein the first set of first signal deliveryparameters includes a pulse width between 25 microseconds and 166microseconds, inclusive.
 18. The system of claim 1 wherein the secondset of second signal delivery parameters includes a pulse width from 10microseconds to 1,000 microseconds, inclusive.
 19. The system of claim 1wherein the controller includes instructions for interleaving one ormore second pulses between sequential bursts of the first pulses. 20.The system of claim 1 wherein the controller includes instructions fordirecting the first pulses to a first electrode of the signal deliverydevice and directing the second pulses to a second electrode of thesignal delivery device different than the first electrode.
 21. Thesystem of claim 1 wherein the controller is programmed with instructionsfor directing the first and second pulses sequentially to a commonelectrode of the signal delivery device.
 22. The system of claim 1wherein the controller is programmed with instructions for directing thefirst and second pulses to a common electrode of the signal deliverydevice, with a single second pulse directed during an interval betweensequential bursts of the first pulses, without the first pulsesoverlapping temporally with the second pulses, and with the first pulseshaving a first pulse width and the second pulses having a second pulsewidth greater than the first pulse width.
 23. The system of claim 1wherein the second pulses include a single second pulse delivered duringan interval between sequential bursts of the first pulses.
 24. Thesystem of claim 1 wherein the controller is programmed with instructionsfor: increasing an amplitude of the first pulses; increasing anamplitude of the second pulses as the amplitude of the first pulses isincreased; and based on patient feedback to the second pulses, changingthe first signal delivery parameters.
 25. The system of claim 1 whereinthe controller is programmed with instructions for changing theamplitudes of the first and second pulses in a parallel manner.
 26. Thesystem of claim 25 wherein the amplitudes of the first and second pulsesare offset, and wherein changing the amplitudes of the first and secondpulses includes changing the amplitudes of the first and second pulsesby different amounts.
 27. The system of claim 1 wherein the controlleris programmed with instructions for identifying a fault with thedelivery of the first pulses based at least in part on the presence orabsence of patient response to changing an amplitude of the secondpulses.
 28. The system of claim 27 wherein identifying a fault is basedat least in part on an absence of a patient response.
 29. A patienttreatment system, comprising: an implantable pulse generator coupleableto an implantable signal delivery device and having a controllerprogrammed with instructions for: directing a first, non-paresthesiagenerating electrical signal to the implantable signal delivery deviceto create an anesthetic effect in a patient, the first electrical signalhaving a first set of first signal delivery parameters, including afrequency in a frequency range from 1.5 kHz to 100 kHz, a pulseamplitude of from 0.5 mA to 10 mA, and a pulse width of from 10microseconds to 333 microseconds; and directing a second electricalsignal to the signal delivery device, the second electrical signalhaving a second set of second signal delivery parameters, including afrequency in a frequency range from 2 Hz to 1.2 kHz.